A-bomb survivors, Atomic Energy Commission - Department of Energy workers, the population exposed to fallout from atmospheric tests at the Nevada Test Site, etc., have been studied for their potential to provide low-dose risk estimates for radiogenic cancer. Only some combination of experimental and theoretical work, with epidemiologic studies at higher doses, will provide a reliable guide to such risks. Sources of variation in risk estimates for radiogenic cancer are explored for their significance to research on carcinogenic mechanisms and to give direction to epidemiologic research. Dr. Beebe serves as Assistant Project Officer for the study of thyroid nodules in the high background area of China. He also represents the Department of Health and Human Services on the Science Panel of the Committee on Interagency Radiation Research and Policy Coordination, and NIH on the Public Health Service Group for Input and Communication Regarding Radiation Protection Activities.